"To be honest, I've never been involved in any of those situations, so I don't know [if trust can be regained]," he told Cosmopolitan magazine in its December issue. "It would be just a guess and a shot in the dark, and I don't want to give that if I haven't even been there myself."

Lautner, 26, said of Stewart: "Kristen is fantastic at everything she does. I'm always proud of her."

When asked in general about reconnecting with one's ex, he said, "I absolutely think it's possible. It depends how long you were with that person. If it was a long, serious relationship, I think it's quite easy to rekindle. I guess it depends on what damage has been done. There's no ex out there who I'm not friends with today, and I'm extremely thankful for that."

Stewart and Pattinson, who broke up following revelations Stewart had cheated on him with her "Snow White and the Huntsman" director Rupert Sanders, recently reconciled.

Lautner, who dated actress Lily Collins, his co-star in last year's "Abduction" until their breakup in September 2011, said he believes that "honesty and loyalty are key. If two people can be honest with each other about everything, that's probably the biggest key to success. I like to think of myself as very loyal, and I love everyone I surround myself with, whether they're friends or girlfriends or whatever. I love loyal people."